Screw lift

ABSTRACT

In a screw lift the lift cage is carried by a drive nut rotatably provided on an essentially upright screw, the lift cage carrying a bearing means and a drive means for the nut. The screw is supported by several supporting braces attached thereto along the length thereof. The nut has the shape of a spiral having turns, the pitch and axial thickness of which are adapted to the distance between the braces and the dimensions of these in the length direction of the screw so as to enable the nut to pass freely past the braces by passing between the turns of the nut during the passage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an arrangement in a screw lift, inwhich the lift cage or similar is carried by a nut rotatably provided onan essentially upright screw, the lift cage carrying a bearing means anda drive means for the nut.

2. Discussion of the Related Art

Conventionally, in such screw lifts, the screw hangs from an attachmentat the uppermost end of a guide rod. This design is limited with respectto its lifting height, since the dead weight of the screw plus the liftcage with its load shall be carried by the screw. Furthermore the guiderod must be designed so as to be able to carry the above mentioned loadplus dynamic additional loads at catching and braking operations.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide, in a screw lift of the kindindicated above, an arrangement that admits an unlimited lifting height.

The above mentioned purpose has been attained in that, according to theinvention, the screw is supported by several supporting braces attachedthereto along the length thereof, and in that the nut has the shape of aspiral having turns, the pitch and axial thickness of which are adaptedto the distance between the braces and the dimension of these in thelength direction of the screw so as to enable the nut to pass freelypast the braces by these passing between the turns of the nut during thepassage.

The invention makes possible location of the screw resting with itslower end on a bed, the task of the braces being to support the screwagainst breaking under the moment imposed by the lift cage plus load.The task of a guide arranged in association with the screw is limited toguidance of the lift cage and taking up moments via lift cage guidingrolls running on the guide.

DESCRIPTION OF THE DRAWINGS

The invention will now be described more closely below with reference tosome embodiments which are shown schematically on the drawings, of which

FIG. 1 a side view of screw and nut together with the driving portion inone embodiment of a screw lift according to the invention;

FIG. 2 is a view in the direction of arrows II--II in FIG. 1;

FIG. 3 is a partly sectional view essentially in the direction ofIII--III in FIG. 2;

FIGS. 4-6 in an elevational view, an end view and a side view,respectively, illustrate a section of a screw used with a screw liftaccording to the invention, the screw being attached to a guide by meansof supporting braces spaced along the length of the screw;

FIG. 7 shows a view in the direction of arrows VII--VII in FIG. 5 of adetail of the screw and guide combination;

FIG. 8 in a heavily enlarged scale shows the encircled portion of thescrew designated VIII in FIG. 6;

FIG. 9 shows a sectional view in the direction of arrows IX--IX in FIG.8;

FIGS. 10 and 11, respectively, in the direction of arrows X--X in FIG. 8show two embodiments of a connecting element included in FIG. 8;

FIG. 12 in a similar view as in FIG. 2 illustrates an alternativedriving method for the drive nut;

FIG. 13 in an axial section through a portion of the nut in a furtherembodiment of the invention illustrates an alternative design of thesupporting braces for the screw; and

FIG. 14 shows the brace according to FIG. 13 in a plan view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the different Figures the same or similarly acting portions haveobtained the same reference characters.

In the Figures the screw of a screw lift is designated 2, the screw liftbeing of the kind where the screw in an essentially upright positioncarries a lift cage which is indicated at 4 in some of the Figures. Asnoted in FIG. 4, the screw 2 with its lower end rests upon a base B. Ina way to be described more closely below, the lift cage 4 carries adrive means, generally designated 6, and a bearing means, generallydesignated 8, for a nut 10 running on the screw 2.

The screw 2 is partitioned in mutually interconnected screw sections 2',2", 2"' (FIGS. 4 and 6). Each screw section 2', 2" and 2"',respectively, is connected with a corresponding guide section 12', 12"and 12"', respectively, of a guide 12 by means of supporting braces 14.Each guide section is a plane and essentially elongated frame workstructure of U-shaped side profile members 16 interconnected by means oftransverse webs 18.

The braces 14 are distributed along the length of the screw 2,preferably so as to be somewhat more closely appearing in connectionwith the joints between the sections. In the example shown in FIGS. 4-6three braces 14 are arranged for each screw section 2', 2", 2"'. In atransverse section each brace 14 is essentially plate shaped with a lowelongated base at 20, which is attached, e.g. by means of welding, to acorresponding one of the transverse webs 18 extending along the wholelength thereof. From the base 20, in the middle thereof, an arm 22 isextending perpendicularly outwardly, at the end of which the screw isattached, e.g. by means of welding or clamping as will be described moreclosely below. The base 20 of the braces 14 extends, of reasons whichwill appear from below, under an angle with the screw 2, whichcorresponds to the pitch of the screw.

The guide sections 12', 12" and 12"' are interconnected at their ends bymeans of screw joints indicated at 24. The guide mast is guided at thejoints by means of special guide buttons 26 so that the panel surfacesof the guide sections are smoothly guided at the joint and a smoothrunning race 23 for each of the guide wheels, to be described below, ofthe lift cage is obtained. Such a guide button 26 is shown more indetail in FIG. 7.

FIG. 8 on an enlarged scale shows the region of the joint between thetwo screw sections 2" and 2"'. According to the embodiment shown in FIG.10 the screwing together of the screw sections is carried through end toend by means of a screw 28 of the rigging screw type with oppositelythreaded end portions 30 and 32, respectively, engaging correspondinglythreaded holes in the end of the screw 2" and 2"', respectively. A midportion 34 of the rigging screw 28 has through holes 36 for receiving aspecial key during the mounting operation, c.f. FIG. 9. The portion 34is then reachable through an indentation 38 in the screw 2"'.

In the embodiment of FIG. 11 a special screw is used for the joiningtogether of the screw sections, one end 40 of which is attached in ahole in the end of the screw 2"' and the other end of which is threadedinto a threaded hole in the end of the screw 2". The interconnectionscrew shown in FIG. 11 likewise has a mid portion 34, 36 of the sameshape and function as in the embodiment shown in FIG. 10, and beingreachable through an indentation corresponding to the indentation 38.With its side remote from the screw 2 the guide 12 may be mounted on awall or similar of a building or construction, in which the lift shallbe used, c.f. the attachment plate indicated at 41 in FIG. 12 as well asthe screw joints indicated there at 41a.

The nut 10 has the shape of a spiral having turns, the pitch and axialthickness a (FIG. 3) of which are adapted to the distance b (FIG. 6)between the braces 14 and the dimension c (FIG. 3) of these in thedirection of the screw 2, so as to allow the nut 10 to pass freely pastthe braces 14 by these passing between the turns of the nut during thepassage. More particularly, this is also obtained by the distance bbeing an even multiple of the pitch of the turns of the nut 10 and bythe above mentioned location of the base 20 at an angle corresponding tosaid pitch.

In FIG. 3 a method for attaching the braces 14 to the screw 2 isindicated at 42, viz. by welding.

In the embodiment shown in FIGS. 1 and 2 the bearing means 8 for the nut10 includes an upper bearing house portion 44 having an indentation, notshown, for allowing passage of the braces 14 during movement of the nutalong the screw. The bearing means 8 also includes a lower bowl shapedbearing house portion 46. The bearing house portions 44, 46 are carriedon the lower side of a plate 48 which is directly or indirectly attachedto the lift cage 4 in a way not shown, e.g. by means of screw joints.The plate 48 includes an indentation 50 adapted to the shape of thebraces 20, 22 for allowing passage of these.

In a way not shown the lift cage 4 furthermore carries a number ofsupport wheels 52, each having an axis 53 and of which one is indicatedin FIG. 2 and two are indicated in FIG. 12. The support wheels run onthe side of the profile members 16 facing the screw. Via the wheels 52the guide carries moments from the lift cage and structure connectedthereto.

The nut 10 has outer teeth 54 by means of which the nut engages adriving tooth wheel 56 which is rotatably supported in the plate 48. Anupper shaft pin 58 connected to the tooth wheel 56 carries a brake drum60 and a lower shaft pin 62 connected to the tooth wheel 56 carries abelt pulley 64. The belt pulley 64 forms part of a belt drive, generallyindicated at 66, by means of which the tooth wheel 56, and thereby thenut 10, is driven by an electric motor 68. The drive means 6 formed bythe elements 56-68 is suspended on the lift cage 4 and structureconnected thereto in a way not shown or described. The man of the artrealizes how to carry this through in practice.

The bearing means for the nut 10 will now be described in more detailwith reference to FIG. 3. In FIG. 3, the parts 44, 48, 70 and the plate47 are joined to each other by suitable connections. For example, theparts 48 and 70 can be bolted to each other, the parts 47 and 70 can bewelded, while the parts 46 and 47 may be bolted to each other. Otherconnection means are also known to those skilled in the art.

The nut 10 is surrounded by two bearing blocks 70 of which one is shownin section in FIG. 3 and two are indicated in FIG. 12. Moreparticularly, the bearing blocks, which are carried in the house portion44, may surround the nut to an extent allowed by the free spaceavailable therefor at the circumference of the nut. This implies thatthe space for threaded engagement between the tooth wheel 56 and the nut10 must be left free, as well as the space where the nut passes thebraces 14. The surface of the bearing blocks 70 intended for cooperationwith the nut 10, and forming part of a cylinder surface, has a number ofribs 72 extending in radial planes and engaging indentations 74 in theouter periphery of the nut 10 correspondingly extending in radialplanes. The lower surfaces of the ribs 72 and the facing surfaces of theindentations 74 form cooperating bearing surfaces by means of which thelift cage and the structure associated therewith is carried by the nut.

By virtue of the fact that the nut, in the way described above, issupported on an enlarged surface, it will not be compressed under load,but distributes the weight and load of the lift cage to the screw overits whole length. By its engagement with the teeth 54 the tooth wheel 56acts as an arresting means for preventing that the turns of the nut 10are mutually twisted.

In the lower bearing house portion 46 a safety nut 76 is arranged whichis likewise in engagement with the screw 2. Normally it does nottransfer any load but is freely co-running when the lift is operated. Ifthe drive nut 10 fails, the load will be carried by the safety nut 76via a friction lining 45 arranged between the house portions 44 and 46,making that the lift stops (self-braking). If a pitch is chosen for thenut and screw combination which implies self-braking, the frictionlining is not needed. As an alternative the lift can be provided with acatch apparatus, implying that the drive need not be self-braking and ahigher velocity of the lift may be allowed.

In the lower end of the nut a pin 82 is inserted. The pin extends into abore in the upper end of the safety nut 76. There is a clearance betweenthe nut and the safety nut. Normally there is no axial load on thesafety nut since the load is taken up by the ribs 72 such that thesafety nut rotates with the nut without being loaded, i.e., it rotatesfreely. However, if a breakage occurs, e.g., of the ribs so that the nutno longer will be supported by them, then the weight of the lift cagewill be transmitted from the nut to the top of the safety nut. Then, thesafety nut will be pressed against the friction lining 45 to therebystop the lift cage from further movements.

The pitch angle of the screw can be chosen so as to make the drive nutself-braking, by giving the screw a large diameter. It is also possibleto choose a smaller diameter for the screw and a greater pitch and let abrake make the drive self-braking. An example of this is the brake drum60 in FIG. 1. The brake is then designed so as to brake less hard duringdrive upwardly as compared with downward movement.

An example of such a brake arrangement is also shown in FIG. 12, whichalso illustrates an alternative to the tooth wheel drive used in theembodiment according to FIGS. 1 and 2. Here the motor 68 drives a beltpulley 82 via a belt drive 80. Over the belt pulley 82 and a co-runningwheel 84 located at a distance therefrom, a tooth belt 86 runs, whichengages the teeth 54 of the nut 10 with a long portion of its length.Apparently a longer driving contact surface is obtained here, ascompared with the embodiment of FIGS. 1 and 2 with the engagagementbetween the tooth wheel 56 and nut 10.

The brake arrangement includes a brake block 88 having a surface ofengagement with an area free of teeth, not shown in FIG. 12, on theperiphery of the nut 10. More particularly, the brake block 88 does notact diametrically against the engagement surface of the nut 10, butunder an angle thereat, implying that the brake block 88 exerts agreater braking force during clockwise rotation of the nut 10, as seenin FIG. 12, as compared with rotation in the other direction. Theclockwise rotation then corresponds to downward movement of the lift.Closer details of the mechanism of engagement of the brake block 88 donot form part of the invention and need therefor not be described here.The realization thereof is, however, evident to the man of the art.

In FIG. 12 also the bearing blocks of the nut are indicated, which, moreparticularly, here are two essentially mutually opposite bearing blocks70. Of course, their available space is limited by the fact that thewheels 82 and 84 and the brake blocks 88 occupy space.

In FIGS. 13 and 14 an alternative form of attachment for the attachmentbraces, here designated 114, is shown. More particularly, eachattachment brace 114 here forms a loop 116 enclosing the screw 2 andextending in a grove 118 in the ridge of the screw 2. The loop 116extends from two arms 120, 122, arranged in parallel above each other,corresponding to the arm 22 of the braces 14 and passing over into eacha base portion having a shape corresponding to the shape of the baseportion 20 of the braces 14.

I claim:
 1. An arrangement in a screw lift, in which a lift cage iscarried by a drive nut rotatably provided on an essentially uprightscrew, the lift cage carrying a bearing means and a drive means for thenut, wherein the screw is supported by several supporting bracesattached thereto along a length thereof, and the nut has the shape of aspiral having turns which have a pitch and an axial thickness which areadapted to a distance between the braces and a dimension of the bracesin a length direction of the screw so as to enable the nut to passfreely past the braces and the braces to pass between the turns of thenut during the passage.
 2. An arrangement according to claim 1, whereinthe screw is partitioned into sections connectable to each other end toend.
 3. An arrangement according to claim 2, further comprising a guidehaving a plurality of guide sections, wherein the screw comprises aplurality of screw sections and each screw section by means of thebraces is attached to an associated guide section which is likewiseconnectable to other guide sections.
 4. An arrangement according toclaim 3, wherein the guide has running races for guide wheels intendedto carry a load of the lift cage and associated structure.
 5. Anarrangement according to any one of the preceding claims, wherein anouter periphery of the nut is provided with teeth intended forengagement with a drive element having teeth.
 6. An arrangementaccording to claim 5, wherein the teeth of the nut extend at least overa considerable portion of the whole length of the nut.
 7. An arrangementaccording to claim 6, wherein the nut between its ends has at least onebearing surface intended for carrying axial forces.
 8. An arrangementaccording to claim 7, wherein said at least one bearing surface isformed by one side of a groove, said one side extending in a peripheryof the nut in a plane perpendicular to the axial direction.
 9. Anarrangement according to claim 8, wherein the nut is supported inbearing blocks having, in a wall thereof facing the nut, a bearingsurface arranged for engagement with each bearing surface of the nut.10. An arrangement according to claim 9, wherein the bearing blocksextend along the length of the nut and have a plurality of ribsextending in radial planes and being intended for engagement with eachof a like plurality of the grooves.
 11. An arrangement according toclaim 10, wherein the screw with its lower end is supported on a base.12. An arrangement according to claim 1, further comprising a brakedevice for making the drive means self-braking.
 13. An arrangementaccording to claim 1, further comprising a brake device for acting moreforcefully at movement downwards than at upwards movement.
 14. Anarrangement according to claim 11, further comprising a safety nutlocated below the drive nut and having the shape of a spiral with thesame characteristics as the drive nut.